The present invention relates to an optical power divider for dividing an optical signal which is transmitted through an optical fiber among a plurality of optical fibers and a method for manufacturing the optical power divider.
With a rapid progress of fiber optic transmission technology, optical data links which use optical fibers for transmitting data between a computer and a computer or between a computer and a terminal have been researched ardently and developed more and more. In the structure of such optical data links, an optical star coupler which is capable of mixing optical signals supplied from a plurality of inputting optical fibers and dividing the mixed optical signals among a plurality of outputting optical fibers equally and with a small loss is an essential device.
One of such devices is disclosed, for example, in U.S. Pat. No. 4,439,221 "METHOD FOR MAKING OPTICAL FIBER COUPLERS" by Smith et al.
In this device, a multiplicity of optical fibers are bundled, twisted under heating, pulled and fused so as to form a tapered region at the central portion of the bundle. This structure enables an optical signal input from one end of an optical fiber to be divided among the other ends of a plurality of optical fibers. In this kind of optical star coupler, however, the tapered region has a very small outer diameter. For example, if the number of optical fibers is several, the outer diameter of the tapered region is several ten .mu.m to one hundred and several ten .mu.m, and even if the number of optical fibers is about one hundred, the outer diameter of the tapered region is only several hundred .mu.m. For this reason, the tapered region is apt to be broken during operation and such an optical star coupler is disadvantageously difficult to handle.
Furthermore, it has been found that when the tapered region which has been processed is put into a practical system as it is, the surface of the tapered region is gradually eroded by the alkaline metal and earth metal ions or the like contained in the air, so that the mechanical strength as well as the optical properties of the system is deteriorated. In addition, the optical properties of the system are deteriorated due to the adhesion of the OH ions, transition metal ions, dust, etc. in the air, and when mechanical vibration is applied to the system, the optical properties are varied due to the above-described adhesion.